Tesla Inc boss Elon Musk said in a filing on Monday he will serve as chief executive of Twitter, the social media company he just bought for $44 billion, a move that Wall Street analysts have said could stretch the billionaire thin.

Musk, who also runs rocket company SpaceX, brain-chip startup Neuralink and tunneling firm the Boring Company, fired Twitter's previous chief, Parag Agrawal, and other top company officials last week.

Tesla's stock has lost a third of its value since Musk made an offer to buy Twitter in April, compared with a 12 per cent decline in the benchmark S&P 500 index in the same period.

Musk had previously changed his Twitter bio to “Chief Twit” in an allusion to his planned move.

Twitter on Monday declined comment on how long Musk might remain CEO or appoint someone else.

In another filing on Monday, Musk revealed that he became the sole director of Twitter as a result of the takeover.

“The following persons, who were directors of Twitter prior to the effective time of the merger, are no longer directors of Twitter: Bret Taylor, Parag Agrawal, Omid Kordestani, David Rosenblatt, Martha Lane Fox, Patrick Pichette, Egon Durban, Fei-Fei Li and Mimi Alemayehou,” Musk said in the filing.

Shortly afterward, Musk tweeted that the move to dissolve the board “is just temporary”, without elaborating.

Last week, Musk's takeover of the social media company for $44bn concluded a months-long saga.

Read: For Twitter boss Musk, now comes the hard part

Since the takeover Musk has moved quickly to put his stamp on Twitter, which he had ridiculed for months for being slow to introduce product changes or take down spam accounts.

His teams began meeting with some employees to investigate Twitter's software code and understand how aspects of the platform worked, according to two sources familiar with the matter.

Some staff who spoke with Reuters said they had received little communication from Musk or other leaders and were using news reports to piece together what was happening at the company.